IMPORTANCE OF PHOSPHORIC ACID 81 



found on Plots 4 for the addition of phosphoric acid. The 

 straw shows just as marked an increase of crop brought about 



Nitrogen 

 only. 



Nitrogen 



and 



Phosphoric 

 Acid. 



Nitrogen 



and 

 Potash, 



Nitrogen, 

 Phosphoric Acid 



and 

 Potash. 



Grain per Acre,!b. 



Straw per Acre,lb. 



FIG. 13. Effect of Mineral Manures on the yield of Barley (Grain and Straw). 

 Mean of Series A, AA, and C. 51 years (1852-1902). 



by phosphoric acid as does the grain, rising from 19 '5 cwt. to 

 25*6 cwt. per acre. In the field the most striking effect is 



